String permutations

Giovanny Gongora

Generates all permutations of a string (contains duplicates).

const stringPermutations: string[] = (str: string) => {
  if (str.length <= 2) return str.length === 2 ? [str, str[1] + str[0]] : [str];
  return str
    .split('')
    .reduce(
      (acc, letter, i) =>
        acc.concat(
          stringPermutations(str.slice(0, i) + str.slice(i + 1)).map(
            val => letter + val
          )
        ),
      []
    );
};